Self-Adhesive, Antibacterial, Highly Stretchable Wearable Sensors Rapidly Fabricated via Deep Eutectic Solvent-Mediated Free-Radical Polymerization

Abstract At present, developing novel gel materials that simultaneously possess favorable environmental adaptability, stable electrical conductivity, and reliable sensing performance has become a critical challenge in the field of flexible sensing. Deep eutectic solvents (DES), as a class of green, low-toxic and nonvolatile novel solvents, feature high ionic conductivity and strong designability, offering a promising strategy to replace the aqueous phase in conventional hydrogels for fabricating conductive gels with environmental adaptability. In this study, urea and choline chloride were first used as raw materials to prepare a deep eutectic solvent. Subsequently, acrylic acid, sodium styrenesulfonate, and sodium chloride were dissolved in the DES, and DES-based conductive gel sensors with wide-temperature adaptability were successfully fabricated via rapid free-radical polymerization. The as-prepared DES gel exhibits long-term stability, antifreezing capability at low temperatures, outstanding sensing performance, as well as antibacterial and self-adhesive properties. It possesses superior mechanical properties with an elongation at break up to 1300%, and remains intact without fracture even under a compressive strain of 99%. Compared with hydrogels, the DES gel achieves remarkable low-temperature performance and maintains stable and excellent working performance even at −20 °C. The results reveal that the gel retains self-adhesion after storage at −80 °C for 12 h; it can adhere to finger joints and withstand bending without rupture. This DES gel is capable of perceiving and detecting mechanical stretching, compression, and multisite human motions, including multiangle bending of finger joints, head nodding, knee stepping, running, and other movements. Moreover, simple digital handwriting recognition and basic gesture recognition can be realized. The gel can be fabricated through a facile and convenient preparation route, and the as-fabricated DES gel integrates multiple excellent comprehensive performances. As a novel, flexible wearable sensing material, it holds great promise for broad applications in advanced flexible sensing systems.